PAKACOlx'Ol'OCA AKERMANI (wARRKn). 339 



two procerebral lobes^ and it is equivalent to the "central 

 body" of same authors (PI. XIX, fig. 54, h.). 



The tritocerebrum arises from the posterior surface of the 

 procerebral lobes (fig. 56, tri.) It is indented by a large 

 tracheal tube. From the tritocorebral lobes there ai'ise the 

 roots of two nerves (r. /. n.) which pass in front of the 

 oesophagus, join together and form a fine median nerve which 

 runs forwards immediately dorsal to the oesophagus and cuds 

 in a small median frontal ganglion, occurring in the plane of 

 the optic lobes (fig. 46, /. g.). 



Posteriorly the tritocerebral lobes bear a lateral rosophageal 

 ganglion (fig. 46 and 56, /. c. g.), and these two ganglia are 

 connected by a transverse commissure (tr. c.) running posterior 

 (ventral) to the (^esophagus. At the junction of the trito- 

 cerebrum and lateral oesophageal ganglion there is given off 

 on each side a large labi^al nerve (fig. 56, la. n.). 



The pi'othoracic ganglion is separated from the sub(jeso- 

 phageal ganglion by only a very short connective, but even 

 this shows division (fig. 46) into right and left. 



The nerves for the 1st pair of walking-legs arise latero- 

 ventrally from the prothoracic ganglion. The mesothoracic 

 ganglion is of about the same size as the prothoracic, and the 

 connectives between the two ganglia are nearly double the 

 length of a ganglion and are quite separate from each other. 



The metathoracic ganglion is somewhat short from back to 

 front, and it is continuous behind with the larg;e elono-ated 

 abdominal ganglionic mass. The two separate connectives 

 between the nieso- and metathoracic ganglia are short, 

 being not more than about half the length of a ganglion. 

 The nerves for the ord pair of walking legs arise ventral ly 

 from the metathoracic ganglion near its junction with the 

 abdominal mass (PI. XIX, fig. 46). 



The abdominal ganglionic mass lies almost entirely in the 

 thorax and consists of the fusion of a number of abdominal 

 ganglia. From the condition of the supposed larva it is clear 

 that there is a strong tendency for the abdominal chain to 

 shorten and to be drawn forward. In the supposed larva 



